Police said the woman was walking down South Lakes near Soapstone about 4:30 p.m. when a man attempted to grab her purse.
The suspect displayed a small knife and a struggle ensued, but the victim was not stabbed.
The suspect fled on foot and was described as Hispanic, about 25 years-old, approximately 5 feet 9 inches tall and 250 pounds, with a mustache and short hair. He was wearing a white T-shirt and blue jean shorts.
In other weekend crime news:
BURGLARY: 11700 block of Karbon Hill Court, Reston, Sunday, 12:50 a.m. A resident reported that she awakened to a man entering her home through a window. The suspect fled in an unknown direction and was described as white, 20 to 30 years old, wearing a white T-shirt and blue jeans.
TRESPASSING: 11000 block of Caris Glenne Drive, Herndon, July 22, 9:30 p.m. A resident reported someone entered their residence and shut off their power. No property was taken.
Moorings Drive/Chatham Colony Court, license plate from vehicle
1400 block of Lake Fairfax Drive, phone from residence
11100 block of North Shore Drive, food from business
8700 block of Potomac Hills Street, purse from vehicle